Floating Windfarms

SOWING THE WIND, POWERING THE FUTURE

"The progression from onshore to offshore to floating wind power pursues a sustainable solution that minimises the environmental impact, yet optimises the power derived."

Nigel Crowe
Business Line Manager of Renewables and Wind, TÜV SÜD

Friday, April 27, 2018

How will we provide for the energy needs of tomorrow? The question has become the great scientific riddle of our times. With many countries now turning their backs on nuclear power and fossil fuels, renewable energy objectives are no longer the stuff of futuristic fancy – they are, instead, a pressing matter for today’s highest-ranking politicians and innovators.

Many argue that wind power could well be one of the solutions for sustainable power generation. It is both cheap and effective, and has the added advantage of having very low environmental impact compared to conventional power sources. With many communities reluctant to sanction the building of wind farms near their homes and the need for volumes beyond the realistic capacities that are viable onshore, some engineers are searching for innovative solutions – leading to the rapid rise of offshore windfarms.

Coastal challenge: A search for solutions at sea

Wind power has been used as a source of energy for thousands of years, with the first wind turbine used to generate electricity dating back more than a hundred years, to 1887 in Scotland. Traditionally, wind farms have been built on land – and many still are. Late last year, Swedish authorities gave the green light to a 650mW onshore wind farm. China’s massive Gansu Wind Farm, meanwhile, has some 7,000 turbines, and will achieve a capacity of 20,000mW by 2020. But in many countries, limited land resources, and topography that disrupts wind flow mean that extremely large utility scale onshore wind farms like Gansu simply are not viable.

Offshore windfarms however, have opened up more possibilities. Located at sea rather than on land, these wind turbines no longer pose a source of conflict for communities. Indeed, in many regions, offshore wind has become an industry in its own right. Per industry group WindEurope, Europe’s current offshore wind capacity is set to almost double in the next two years, reaching a combined 25GW by 2020. In fact, 2017 was a record year for offshore wind power in Europe, with 4,000 offshore turbines now operating across 11 countries.

However, the challenge with conventional offshore windfarms is that it requires a shallow seabed of water depths up to approximately 50 meters for turbines to be mounted. Globally, the coastlines with this shallow water depth are limited. These areas often have the most traffic from ships, are crossed by cables, and contain the most environmentally sensitive sea life.

“The proportion of the seas that this water depth exists is very small. Moving further opens up huge further potential for wind power generation,” explains Nigel Crowe, Business Line Manager of Renewables and Wind at TÜV SÜD. The introduction of floating windfarms has the potential to change this dynamic. When turbines are placed further offshore, they benefit from faster, steadier and therefore more usable wind.

Out at sea

If you want to build a truly effective wind farm, it needs to be positioned in a place where wind speeds remain as high as possible. “The power that can be extracted from the wind has an exponential relationship to wind speed”, says Crowe, “meaning that by doubling wind speed, you end up generating up to eight times as much power,” he elaborates.

Crowe continues, “Working further offshore avoids the reduction in wind speed that comes from urban structures and the physical blockages that the land presents even a few kilometres from the coast.”

What is more, being able to move farms further out means there is more flexibility in siting wind farms. Energy professionals can thus search for locations that are less disruptive to coastal residents, where they create less noise pollution, are less of a nuisance for ports and shipping, and – importantly – where they pose least threat to sea life.

Unfortunately, building an offshore floating wind farm is harder than it may seem. Crowe explains, “As wind farms float on the sea, they pose some unique challenges. Keeping turbines vertical enough to remain functional can be challenging, as the forces trying to bend them over are so powerful. Large, innovative, floating foundations are required.”

Fortunately, says Crowe, modern technology, and design is now allowing planners to seriously consider moving wind farms further out to sea. He notes, “New applications allow for more efficient power storage. And floating wind farms can now be constructed close to the shore before being towed out by low cost ships, avoiding the need to use expensive vessels to construct turbines on fixed foundations.”

Safety first

It is still early days for floating wind power. But as nations around the world pledge themselves to renewable energy commitments through agreements such as the Kyoto Protocol, planners and administrators are now under pressure to get wind farms up and operational as soon as possible. This means that greater care than normal must now be taken to ensure that safety is not compromised at new wind farms.

Crowe adds, “Wind turbines are maintained in a way that is becoming aligned to the management of commercial jet engines. In order to provide reliable, safe and efficient operation, they require effective, targeted and rigorous testing and inspection – both by manufacturers and third-party inspection providers.”

In the wind

Whilst offshore wind power is entering its mature phase, floating offshore wind power still has significant development till it can be seen as mainstream. But the future is bright for this increasingly effective way of reaping energy from the high-sea winds that have both helped and hindered humankind since the dawn of time.

Floating windfarms that were regarded as a futuristic technology have now been realised. The world’s very first floating windfarm has just opened in 2017. Hywind Scotland, located off the coast of Scotland, is expected to power over 20,000 homes in the United Kingdom (UK).

The speed of development has provided confidence that we are taking the right steps to manage the Energy Trilemma. Addressing energy equity, one of the core dimensions of the Energy Trilemma, Crowe says, “As deep-sea wind farms apply young technologies that are yet to be widely applied, costs remain relatively high. But, as we have seen with onshore farms, bottom-mounted offshore projects and solar power, as technology develops, costs fall significantly.”

What does the future hold for wind energy? “The biggest breakthrough’s in floating offshore wind power will come with the development of effective storage solutions, so that the distance from the point of use will become immaterial,” says Crowe.